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      <h2>8.4: onListSelection&nbsp;<a href="User guide8.html"><img src="Images/uparrow.png" border="0" align="top" alt="Go back up one level"/></a></h2>
      
            <p>Finally, let's have a look at how one of the callbacks works: "onListSelection", the function
        that is called when an item is selected in the listbox. The other
            callbacks obey the same pattern.</p>
            <p>The basic rule of thumb is that a callback should not update any part of
        the user interface directly - it's job is to respond to user interaction by changing the "data" structure. 
        In this example, each callback changes the underlying data structure
    then asks the interface to refresh. This might mean that things update in the
interface that don't need to, but ensures the callbacks remain simple and that all
interface update logic is in one place. Extending this to more granular interface updates
            is straightforward. See <a href="demoBrowserScalability.html">Scalability</a> for more details.</p>
            <p>For the listbox callback, the "src" argument is a handle to the
            listbox and we simply need to update the SelectedDemo field of "data"
            to reflect the new selection. We then ask the rest of the interface to
            update in response to the change.
            </p>
            <example><pre style="background-color: #eeeeff; margin-left: 20px; margin-right: 20px"><font color="#000011">
                <code class="COMMENT">% User selected a demo from the list - update "data" and refresh</code>
data.SelectedDemo = <a href="matlab:doc get"><code class="FUNCTION">get</code></a>( src, <code class="STRING">'Value'</code> );
updateInterface();
redrawDemo();</font></pre>
        <p style="background-color: #ddddee; margin-left: 20px; margin-right: 20px"><font color="#000022"><center><img src="Images/demoBrowser4.png"/></center></font></p>
        </example>
                 <p><small>(Full source code for this application is available here: 
                     [ <a href="Examples/demoBrowser.m">view</a>
                     | <a href="matlab: edit(fullfile(layoutRoot,'layoutHelp','Examples','demoBrowser.m'))">edit</a>
                     | <a href="matlab: p=pwd();cd(fullfile(layoutRoot,'layoutHelp','Examples')); demoBrowser; cd(p)">run</a> ]
                 )</small></p>
        
      
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